2 lbs tri-tip steak, cut into 1/4-lb pieces and trimmed of fat
1 cup shio koji
2 bunches mustard greens
1 shallot, minced
2 cloves garlic, crushed
1/2 cup olive oil, divided
1 tbsp butter (optional)
Rinse the meat under cold water and pat dry with a paper towel. In a nonreactive bowl, combine the meat and the shio koji, cover, and place in the fridge overnight. Meat should be marinated for at least 3 hours and up to 24 hours for optimum tenderness and flavor.
Thirty minutes before you plan to serve, preheat the oven to 450 F. De-rib, wash, and dry the mustard greens. Add the shallot, garlic, and 2 tablespoons olive oil to a wide skillet or pot. Cook on medium heat until translucent, about 4 to 5 minutes. Add the greens and turn the heat down to medium low, slowing braising the greens. Add a little more olive oil (or water) if the mix looks dry.
Remove the meat from the marinade and rinse it off, then pat it dry again. Heat the butter and olive oil in a cast iron skillet. Add the meat as the oil begins to smoke and cook for about 3 minutes per side, until caramel in color.
Once the meat is seared, transfer the skillet to the oven to finish cooking. For medium rare, cook to 140 degrees. Remove the skillet and allow the steak to rest for at least 10 minutes. Slice each piece against the grain for the best texture. Serve with the mustard greens.